This change can be invoked from any of the Microsoft Office apps, and the theme change applies to all other Microsoft Office apps too.
How to Change Microsoft Office (Word, Excel, Powerpoint) Theme on Mac. Mac OS X defaults to a predefined set system font size for all onscreen text and user interface elements, and while many users will find the default text size to be sufficient, some users may wish the system font size was larger, and some may wish the Mac system text size was smaller.
